Multi-stage gas generators with propellant charges which are able to be ignited independently of each other can generate different quantities of gas, coordinated with vehicle occupants or accident-specific parameters. If only one propellant charge is ignited, the outflowing hot gas automatically heats the outer and inner walls, however, so that heat is passed on to the non-ignited propellant charge. Theoretically, this can lead to the non-ignited propellant charge igniting itself after a few minutes, owing to the relatively slow heat transport. This involves dangers both for the occupant who is still to be found in the vehicle and also for rescue personnel.